Baxi Combi 80 Maxflue User guide

Baxi Combi 80 Maxflue
Gas Fired Wall Mounted Combination Boiler
Installation and
Servicing Instructions
Please leave these instructions with the user

2
Baxi UK Limited is one of the leading manufacturers
of domestic heating products in the UK.
Our first priority is to give a high quality service to our
customers. Quality is designed into every Baxi
product - products which fulfil the demands and needs
of customers, offering choice, efficiency and reliability.
To keep ahead of changing trends, we have made a
commitment to develop new ideas using the
latest technology - with the aim of continuing to make
the products that customers want to buy.
Everyone who works at Baxi has a commitment to
quality because we know that satisfied customers
mean continued success.
We hope you get a satisfactory service from Baxi. If
not, please let us know.
Natural Gas
Baxi Combi 80 Maxflue
G.C.No47 075 07
Baxi is a BS-EN ISO 9001
Accredited Company
The boiler meets the requirements of Statutory Instrument
“ The Boiler (Efficiency) Regulations 1993 No3083” and is
deemed to meet the requirements of Directive 92/42/EEC
on the energy efficiency requirements for new hot water
boilers fired with liquid or gaseous fuels:-
Type test for purpose of Regulation 5 certified by:
Notified Body 0051.
Product/Production certified by:
Notified Body 0051.
For GB/IE only.

3
1.0 Introduction 4
2.0 General Layout 5
3.0 Appliance Operation 6
4.0 Technical Data 7
5.0 Dimensions and Fixings 8
6.0 System Details 9
7.0 Site Requirements 12
8.0 Installation 18
9.0 Commissioning the Boiler 23
10.0 Completion 25
11.0 Servicing the Boiler 26
12.0 Changing Components 28
13.0 Illustrated Wiring Diagram 37
14.0 Fault Finding 38
15.0 Short Parts List 43
Section Page
Contents

Baxi UK Limited declare that no substances
harmful to health are contained in the
appliance or used during appliance
manufacture.
1.1 Description
1. The Baxi Combi 80 Maxflue is a fully automatic
gas fired wall mounted combination boiler. It is
room sealed and fan assisted, and will serve
central heating and mains fed domestic hot water.
2. The boiler is set to give a maximum output of
24.0 kW for hot water and central heating.
3. It is designed for use on Natural Gas (G20) and
can be converted to use Propane or Butane.
4. The boiler is suitable for use only on fully
pumped sealed heating systems. Priority is given
to domestic hot water.
5. The boiler data badge gives details of the
model, serial number and Gas Council number
and is situated on the control box. It is visible when
the case front panel is removed (Fig. 1).
6. The boiler is intended for use with an 80mm
diameter twin flue system. The system must be
installed in conjunction with a single roof terminal
or two separate flue and air terminals.
7. Separate terminals do not have to be on the
same wall but must not be on opposite walls of the
dwelling.
8. The separate terminals allow greater flexibility
when siting the boiler - see Sections 7.8 to 7.13 of
Site Requirements for full details of available flue
components, maximum lengths etc.
9. The boiler is intended to be installed in
residential / commercial / light industrial E.M.C.
environments on a governed meter supply only.
10. All systems must be thoroughly flushed
and treated with inhibitor (see section 6.2).
1.2 Installation
1. The appliance is suitable for installation only in
G.B. and I.E. and should be installed in
accordance with the rules in force. For Ireland
install in accordance with I.S.813 “INSTALLATION OF
GAS APPLIANCES”. The installation must be carried
out by a CORGI Registered Installer or other
competent person and be in accordance with the
relevant requirements of GAS SAFETY (Installation
and Use) REGULATIONS, the BUILDING REGULATIONS
(Scotland) (Consolidation), the LOCAL BUILDING
REGULATIONS, the CURRENT I.E.E. WIRING
REGULATIONS and the bye laws of the Local Water
Undertaking. Where no specific instructions are
given, reference should be made to the relevant
BRITISH STANDARD CODES OF PRACTICE.
1.3 Optional Extras
Various control accessories, LPG conversion kits
etc. are available as optional extras. These are
detailed in a separate publication.
1.0 Introduction
4
Data Badge
Fig. 1
Control Box
“Benchmark”Log Book
As part of the industry-wide “Benchmark”initiative all Baxi boilers now
include an Installation, Commissioning and Service Record Log Book.
Please read the Log Book carefully and complete all sections relevant to
the appliance and installation. These include sections on the type of
controls employed, flushing the system, burner operating pressure etc.
The details of the Log Book will be required in the event of any warranty
work. Also, there is a section to be completed at each subsequent regular
service visit. The Log Book must be left with the user.
Case Front Panel
NOTE: This appliance must be installed
in accordance with the manufacturer’s
instructions and the regulations in force.
Read the instructions fully before
installing or using the appliance.

2.0 General Layout
5
2.1 Layout
1. Air Pressure Switch
2. Expansion Vessel
3. Burner Manifold
4. Automatic Air Vent
5. DHW Plate Heat Exchanger
6. Circulation Pump
7. Drain Off Point
8. Pressure Relief Valve
9. Position For Optional Integral Timer
10. Central Heating System Pressure Gauge
11. PCB
12. Control Box
13. 3-Way Valve Assembly
14. Flame Sensing Electrode
15. Spark Electrode
16. Burner
17. Primary Heat Exchanger
18. Fan Assembly
19. On/Off/Reset Selector Switch
20. Central Heating Temperature Control
21. Hot Water Temperature Control
22. Flame Failure
23. Safety Thermostat
24. Fault on Fan or Flue
25. Fault on Pump or Low System Pressure
26. Fault on Hot Water Sensor
27. Fault on Central Heating Sensor
28. Power On
29. Hot Water Mode
30. Central Heating / Hot Water Mode
31. Burner On
When neons 22 to 27 are constantly illuminated,
they indicate the temperature of the central heating
water.
18
17
16
14
15
13
12 11
10 9
19 20 21 10 9
7
6
3
4
5
8
2
1
30°40°50°60°70°80°
2
1
0
4
3
bar
30°40°50°60°70°80°
22 23 24 25 26 27
28 29 30 31

3.0 Appliance Operation
6
NOTE: All delay timers mentioned in 3.1 and
3.2 are overridden by domestic hot water
demand.
3.1 Central Heating Mode (Fig. 2)
1. With a demand for heating, the pump circulates
water through the primary circuit. At a flow rate of
approximately 125 l/hr the central heating flow
switch operates, initiating the ignition sequence.
2. The main burner ignites at low rate, then the
gas valve controls the gas rate to maintain the
heating temperature measured by the thermostat
sensor.
3. When the flow temperature exceeds the setting
temperature, a 3 minute delay occurs before the
burner relights automatically (anti-cycling). The
pump continues to run during this period.
4. When the demand is satisfied the burner is
extinguished and the pump continues to run for a
period of 3 minutes (Pump Overrun).
3.2 Domestic Hot Water Mode (Fig. 3)
1. Priority is given to the domestic hot water
supply. A demand at a tap or shower will override
any central heating requirement.
2. The flow of water will operate the DHW flow
switch which causes the 3 way valve to change
position. This will allow the pump to circulate the
primary water through the DHW plate heat
exchanger.
3. The burner will light automatically and the
temperature of the domestic hot water is
controlled by the thermostat sensor.
4. When the domestic hot water demand ceases
the burner will extinguish and the diverter valve
will remain in the domestic hot water mode,
unless there is a demand for central heating.
IMPORTANT: When the selector switch is in
the ‘0’(Off) position the electrical supply to the
boiler is isolated. The boiler will not operate
and the integral timer (if fitted) will require
resetting once the selector switch is set to
either the DHW position or CH position.
3.3 Frost Protection Mode
1. The frost protection mode is integral to the
appliance and functions only with the selector
switch (see Section 2.1) in the domestic hot water
and central heating position. If the system
temperature falls below 5°C then the boiler will
fire on its minimum setting until a flow temperature
of 30°C is reached. Further protection can be
incorporated by using a system frost thermostat.
3.4 Pump Protection
1. With the selector switch (see Section 2.1) in
either the central heating or central heating and
hot water position the pump will automatically
operate for 1 minute in every 24 hours to prevent
sticking
1
2
4
5 6
7
8
9
10
11
1213141516
17
18
19
20
21
22
23
24
25
26
3
1 Primary Heat Exchanger
2 Burner
3 Ignition Electrode
4 Flame Sensing Electrode
5 Gas Valve
6Pump
7 Automatic Air Vent
8 Plate Heat Exchanger
9 Flow Sensor with Filter
10 Pressure Relief Valve
11 Boiler Drain Point
12 Heating Return
13 Cold Water Inlet On/Off Valve and Filter
14 Gas Inlet
15 Domestic Hot Water Outlet
16 Heating Flow
17 Pressure Gauge
18 Hydraulic Differential Pressure Sensor Microswitch
19 Automatic By-Pass
20 Hydraulic Differential Pressure Sensor
21 Diverter Valve Assembly
22 Domestic Hot Water Flow Priority Assembly
23 Domestic Hot Water Flow Priority Microswitch
24 Overheat Thermostat
25 Central Heating NTC Sensor
26 Expansion Vessel
27 Domestic Hot Water NTC Sensor
Key
Central Heating Circuit
Domestic Hot Water Circuit
Fig. 3
1
2
4
5 6
7
8
9
10
11
1213141516
17
18
19
20
21
22
23
24
25
26
3
Fig. 2
27
27

4.0 Technical Data
7
Flue Terminal Diameter 80mm
Dimensions Projection 80mm
Outercase Dimensions
Casing Height - 780mm
Overall Height Inc Flue
Elbow - 980mm
Casing Width - 450mm
Casing Depth - 345mm
Clearances
Both Sides 5 mm Min
Above Casing 200 mm Min
Below Casing 200 mm Min
Front 450 mm Min (For Servicing)
Front 5 mm Min (In Operation)
Weights kg
Packaged Boiler Carton 47.5
Packaged Flue Kit 2.5
Installation Lift Weight 39.5
Central Heating Primary Circuit
Pressures
bar
Safety Discharge 3
Max Operating 2.5
Min Operating 0.5
Recommend Operating 1-2
DHW Circuit bar
Pressures
Max Operating 8
Min Operating 0.2
Min Operating Pressure
at 9.8 l/min 0.9
Flow Rates l/min
DHW Flow Rate
@ 30o C Rise 13.7
DHW Flow Rate
@ 35o C Rise 9.8
Min Working
DHW Flow Rate 2.5
Pump
Available Head See graph below
Expansion Vessel - (For Central Heating
only. Integral with appliance)
bar
Min Pre-charge Pressure 0.5
litre
Max Capacity of
CH System 125
Primary Water Content
of Boiler (unpressurised) 1.0
Connections copper tails
Gas Supply - 22mm
Central Heating Flow - 22mm
Central Heating Return - 22mm
Cold Water Mains Inlet - 15mm
DHW Flow - 15mm
Pressure Relief Discharge - 15mm
Temperatures
C.H. Flow Temp (adjustable)
35°C to 85°C max (± 5°C)
D.H.W. Flow Temp (adjustable)
35°C to 65°C max (± 5°C)
dependent upon flow rate
Heat Input C/H & DHW (Gross)
kW 26.3 Max
Btu/h 89,739 Max
Heat Output Max Min
kW 24.0 9.3
Btu/h 81,891 31,730
Electrical Supply 230V~ 50Hz
(Appliance must be connected to an
earthed supply)
Power Consumption 170W
External Fuse Rating 3A
Internal Fuse Rating
Fuse 2A Fast Blow to BS 4265
Appliance Category CAT II 2H 3+
Max Gas Rate (Natural Gas)
(After 10 Mins)
m3/h 2.78
ft3/h 98.12
Inlet Pressure (Natural Gas)
mbar 20
in wg 8
Burner Injector (Natural Gas)
15 x 1.18mm Diameter
Burner Pressure (Natural Gas)
Max Rate Min Rate
mbar 10.6 ± 0.5 1.9 ± 0.2
in wg 4.24 ± 0.2 0.76 ± 0.2
0
200 400 600 800 1000 1200
0.5
1
1.5
2
2.5
3
3.5
4
Metre wg
l/h
Pump - Available Head
0
Appliance Type C12 C32 C52 NOxClass 3
This value is used in the UK Government’s Standard
Assessment Procedure (SAP) for energy rating of dwellings.
The test data from which it has been calculated have been
certified by 0051.
SEDBUK Declaration For Combi 80 Maxflue
The seasonal efficiency (SEDBUK) is 78.5 %
Electrical Protection
IPX5D
4.1 Combi 80 Maxflue
LPG Gases Propane - G31 and
Butane - G30
Burner Injector 15 x 0.69
Burner Pressure Max Rate Min Rate
Propane mbar 35.8 6.2
in wg 14.3 2.5
Butane mbar 28.0 4.7
in wg 11.2 1.9
Inlet Pressures Propane Butane
mbar 37 30
in wg 14.8 12

5.0 Dimensions and Fixings
8
Dimensions
A780mm
B345mm
C450mm
Domestic Hot
Water Outlet
(15mm)
Cold Water
Inlet
(15mm)
Heating
Return
(22mm)
Heating
Flow
(22mm)
Pressure Relief
Valve
(15mm)
Gas
Inlet
(22mm)
65 mm 65 mm 65 mm 65 mm 65 mm
Tap Rail
A
C
B

6.0 System Details
9
6.1 Information
1. The Baxi Combi 80 Maxflue Combination Boiler
is a ‘Water Bylaws Scheme - Approved Product’.
To comply with the Water Bylaws your attention is
drawn to the following installation requirements
and notes (IRN).
a) IRN 001 - See text of entry for installation
requirements and notes.
b) IRN 302 - Bylaw 14.
2. Reference to the WRC publications, ‘Water fittings
and materials directory’and ‘Water supply bylaws
guide’give full details of bylaws and the IRNs.
6.2 Central Heating Circuit
1. The appliance is suitable for fully pumped
SEALED SYSTEMS ONLY.
Treatment of Water Circulating Systems
•All recirculatory water systems will be subject to
corrosion unless an appropriate water treatment is
applied. This means that the efficiency of the
system will deteriorate as corrosion sludge
accumulates within the system, risking damage to
pump and valves, boiler noise and circulation
problems.
•For optimum performance after installation this
boiler and its associated central heating system
must be flushed in accordance with the guidelines
given in BS 7593 “Treatment of water in domestic
hot water central heating systems”.
•This must involve the use of a proprietary
cleanser, such as BetzDearborn Sentinel X300 or
X400, or Fernox Superfloc. Full instructions are
supplied with the products, but for immediate
information please contact BetzDearborn (0151
420 9563) or Fernox (01799 550 811) directly.
•For long term protection against corrosion and
scale, after flushing it is recommended that an
inhibitor such as BetzDearborn Sentinel X100, or
Fernox MB-1 or Copal is dosed in accordance with
the guidelines given in BS 7593.
Failure to flush and add inhibitor to the system
may invalidate the appliance warranty.
•It is important to check the inhibitor
concentration after installation, system modification
and at every service in accordance with the
manufacturer’s instructions. (Test kits are available
from inhibitor stockists.)
•For information or advice regarding any of the
above contact Baxi Technical Enquires.
6.3 Bypass
1. The boiler is fitted with an automatic integral
bypass.
6.4 System Control
1. The boiler is designed for use in a heating
system that incorporates external controls, i.e. a
minimum of a timer device.
2. Suitable timer kits are available as optional
extras.
3. For optimum operating conditions and maximum
economy the fitting of a programmable room
thermostat, such as the Baxi Combi Controller, is
recommended.

Stop
Valve
Double
Check
Valve
DHW
Mains
Inlet
CH
Return
Temporary
Hose
6.0 System Details
10
6.5 System Filling and Pressurising
1. A filling point connection on the central heating
return pipework must be provided to facilitate
initial filling and pressurising and also any
subsequent water loss replacement/refilling.
2. There are connection points on the mains cold
water inlet and central heating return isolating
taps (Fig. 4a) to which the optional filling loop kit
(Part No. 248221) can be assembled.
3. The filling method adopted must be in
accordance with the Water Supply (Water
Fittings) regulations and the Water Bylaws
(Scotland).
4. Your attention is drawn to: Paragraph 24 of
Schedule 2 Section 8 of the publication Water
Regulations Guide which gives recommendations
and guidance on approved methods for filling
sealed systems.
5. The sealed primary circuits may be filled or
replenished by means of a temporary connection
between the primary circuit and a supply pipe
provided the arrangement in accordance with
Diagram R24.2a of the Water Regulations Guide.
6. The temporary hose must be completely
removed at both ends after use.
6.6 Expansion Vessel
(Central Heating only)
1. The appliance expansion vessel is pre-charged
to 0.5 bar. Therefore, the minimum cold fill
pressure is 0.5 bar. The vessel is suitable for
correct operation for system capacities up to 125
litres. For greater system capacities an additional
expansion vessel must be fitted - refer to BS 7074
Pt 1.
6.7 Pressure Relief Valve (Fig. 5)
1. The pressure relief valve is set at 3 bar,
therefore all pipework, fittings, etc. should be
suitable for pressures in excess of 3 bar.
2. The pressure relief discharge pipe should be
not less than 15mm dia, run continuously
downward, and discharge outside the building,
preferably over a drain. It should be routed in
such a manner that no hazard occurs to
occupants or causes damage to wiring or
electrical components. The end of the pipe should
terminate facing down and towards the wall.
3. The discharge must not be above a window,
entrance or other public access. Consideration
must be given to the possibility that boiling
water/steam could discharge from the pipe.
Fig. 4
Fig. 5
Pressure Relief Valve
Discharge Pipe
Stop
Valve
Filling Loop
Fig. 4a

6.0 System Details
11
6.8 Domestic Hot Water Circuit (Fig. 6)
1. All DHW circuits, connections, fittings, etc.
should be fully in accordance with relevant
standards, the Water Supply (water fittings)
Regulations and the Water Bylaws (Scotland).
2. Your attention is drawn to:
Schedule 2, Section 6 of the publication Water
Regulations Guide which relates to backflow
prevention.
3. A single check valve must be fitted as shown in
Fig. 6 to prevent backflow to the supply pipe and
to ensure the efficient operation of the expansion
vessel which is required to accommodate the
thermal expansion of the water.
4. When the domestic water system includes any
device which prevents water expanding back
towards the supply (check valve, loose jumpered
stopcock, water meter, water treatment device)
then an expansion vessel must be fitted (eg.
Zilmet 160ml, R1/215bar).
5. If the hot water expansion is not provided for,
then high pressures can develop which may
result in damage to fittings and devices on the
system.
6. The boiler’s maximum working mains pressure
is 8 bar, therefore all pipework, connections,
fittings, etc. should be suitable for pressures in
excess of 8 bar. A pressure reducing valve must
be fitted for pressures in excess of 8 bar. The
manufacturer of any outlet fittings, such as a
shower valve, may require a lower maximum
pressure. The pressure reduction must take
account of all fittings connected to the DHW
system.
6.9 Showers
1. If a shower control is supplied from the
appliance it should be of the thermostatic or
pressure balanced type. Thermostatic type
shower valves provide the best comfort and
guard against water at too high a temperature.
Existing controls may not be suitable - refer to the
shower valve manufacturer.
6.10 Hard Water Areas
1. If the area of the installation is recognised as a
HARD WATER AREA then a suitable device
should be fitted to treat the mains water supply to
the boiler.
Boiler
Other Tap
Outlets
Expansion
Vessel
To Hot
Taps
Check
Valve
Pressure
Reducer Valve
Stop Tap
Fig. 6

7.0 Site Requirements
12
7.1 Information
1. The installation must be carried out by a CORGI
Registered Installer or other registered competent
person and be in accordance with the relevant
requirements of the current GAS SAFETY (Installation
and Use) REGULATIONS, the BUILDING REGULATIONS
(Scotland)(Consolidation), the LOCAL BUILDING
REGULATIONS, the current I.E.E. WIRING REGULATIONS
and the bye laws of the LOCAL WATER UNDERTAKING.
Where no specific instruction is given reference
should be made to the relevant BRITISH
STANDARD CODES OF PRACTICE. For Ireland
install in accordance with IS 813 “INSTALLATION OF
GAS APPLIANCES”.
7.2 B.S. Codes of Practice
Standard Scope
BS 6891 Gas Installation.
BS 5546 Installation of hot water supplies for
domestic purposes.
BS 5449 Part 1 Forced circulation hot water systems.
BS 6798 Installation of gas fired hot water boilers.
BS 5440 Part 1 Flues.
BS 5440 Part 2 Ventilation.
BS 7074 Expansion vessels and ancillary
equipment for sealed water systems.
BS 7593 Treatment of water in domestic hot water
central heating systems.
WARNING - The addition of anything that may
interfere with the normal operation of the
appliance without the express written permission
of Baxi UK Limited could invalidate the appliance
warranty and infringe the GAS SAFETY (Installation
and Use) REGULATIONS.
7.3 Clearances (Figs. 7 & 8)
1. A flat vertical area is required for the installation
of the boiler.
2. These dimensions include the necessary
clearances around the boiler for case removal,
spanner access and air movement. Additional
clearances may be required for the passage of
pipes around local obstructions such as joists
running parallel to the front face of the boiler.
7.4 Ventilation of Compartments
1. Where the appliance is installed in a cupboard or
compartment, no air vents are required as the
appliance runs sufficiently cool.
2. The minimum clearances must be adhered to and
the cupboard or compartment big enough to house
only the boiler and any ancillary equipment.
200mm Min
780mm
450mm
200mm Min
5mm Min
5mm Min
5mm Min
450mm Min
For Servicing
Purposes
Fig. 7
Fig. 8
5mm both sides
recommended for
ease of installation
and service.
In Operation

7.0 Site Requirements
13
7.5 Location
1. The boiler may be fitted to any suitable internal
or external wall. It is primarily intended for use
with a twin flue system using separate horizontal
terminals. It may also be fitted with a vertical twin
flue system connected to a single vertical
terminal. The terminal(s) must pass through an
outside roof (vertical) or wall (separate
horizontal), discharging to atmosphere in a
position permitting satisfactory removal of
combustion products and providing an adequate
air supply. The boiler should be fitted within the
building unless otherwise protected by a suitable
enclosure i.e. garage or outhouse. (The boiler
may be fitted inside a cupboard-see Section 7.4).
2. If the boiler is sited in an unheated enclosure
then it is recommended to leave the ON/OFF
Selector Switch in the domestic hot water and
central heating position to give frost protection.
3. If the boiler is fitted in a room containing a bath
or shower reference must be made to the current
I.E.E. WIRING REGULATIONS and BUILDING
REGULATIONS. If the boiler is to be fitted into a
building of timber frame construction then
reference must be made to the current edition of
Institute of Gas Engineers Publication IGE/UP/7
(Gas Installations in Timber Framed Housing).
4. Separate terminals may be located on the
same or different walls as required, but they must
not be on opposing walls. For example if one
terminal is on a north facing wall the other
terminal may be on the west, east or north wall
but not the south (Fig. 9).
7.6 Gas Supply
1. The gas installation should be in accordance
with BS6891.
2. The connection to the appliance is a 22mm
copper tail located at the rear of the gas service
cock (Fig. 10).
3. Ensure that the pipework from the meter to the
appliance is of adequate size. Do not use pipes of
a smaller diameter than the boiler gas connection
(22mm).
7.7 Electrical Supply
1. External wiring must be correctly earthed,
polarised and in accordance with current I.E.E.
WIRING REGULATIONS.
2. The mains supply is 230V ~ 50Hzfused at 3A.
NOTE: The method of connection to the
electricity supply must facilitate complete
electrical isolation of the appliance.
Connection may be via a fused double-pole
isolator with a contact separation of at least
3mm in all poles and servicing the boiler and
system controls only.
Fig. 10
Gas Service Cock
Fig. 9
Plan view of boiler showing
acceptable terminal locations

Appliance
Input (kW)
0-7
7-14
14-32
over 32
0-7
7-14
14-32
over 32
0-7
7-14
14-32
over 32
Air Terminal
Position
Above a
Terminal
Below a
Terminal
Horizontally
to a Terminal
7.0 Site Requirements
14
7.8 Flue & Air Terminals
1. The flue terminal position must always be
in accordance with the current edition of B.S.
5440 Part 1, and either Part J of the Building
Regulations England and Wales or Part F of
the Building Standards (Scotland)
Regulations as appropriate.
2. The positioning of the air terminal (separate
terminal systems only) is not as critical as that of
the flue terminal except with respect to other flue
terminals, including that of the appliance the air
terminal is serving.
3. When positioning the air terminal general
reference should be made to BS 5440 Pt. 2.
Specifically the air terminal must be separated
from any other flue terminal by at least the
dimensions given in Table 1.
4. The air terminal must draw directly from
outside. It is not permissible to locate it in a loft
space, compartment or similar even when there is
adequate ventilation.
5. See Section 7.5 “Location”for details of which
walls the terminals may be located on. Minimum
clearances from the flue terminal are given in Fig.
11 and the accompanying table.
6. If the flue terminal discharges onto a pathway
or passageway, check that combustion products
will not cause a nuisance. Ensure that any
terminal will not obstruct any pathway or
passageway.
7. If a terminal is less than 2 metres above a
balcony, above ground or above a flat roof to
which people have access, then a suitable
terminal guard must be provided. This also
applies to the air terminal where provision of the
guard will prevent damage or blockage, rather
than the protection of persons from hot flue
gases.
8. The terminals must be positioned such that
they will not become obstructed by leaves, snow
or similar and not be subject to rain entry.
Fig. 11
L
G
G
E
J
D
K
G
AAD
F
H,I
B,C
F
Likely flue positions requiring
a flue terminal guard
M
N
Natural
Draught
300
600
1500
2000
300
300
300
600
300
400
600
600
Fanned
Draught
300
300
300
300
300
300
300
300
300
300
300
300
Separation in mm from
another terminal
Table 1 Note: “Appliance Input”refers to any other appliance
as well as the one served by the air terminal
300 min
Terminal
Assembly
Top View Rear Flue
Property Boundary Line
Terminal Position with Minimum Distance (Fig. 11) (mm)
A Directly below an openable window, air vent or any other
ventilation opening. 300
B Below gutter, drain/soil pipe. 25
C Below eaves. 25
D Below a balcony/car port roof. 25
E From vertical drain pipes and soil pipes. 25
F From internal or external corners. 25
G Above adjacent ground or balcony level. 300
H From a surface facing a terminal. 600
I Facing a terminals. 1200
J From opening (door/window) in carport into dwelling. 1200
K Vertically from a terminal on the same wall. 1500
L Horizontally from a terminal on the same wall. 300
M Above an opening, air brick, opening window etc. 300
N Horizontally to an opening, air brick, opening window etc. 300

7.0 Site Requirements
15
7.9 Flue Connections
1. The flue duct adaptor, air duct adaptor, 90°
male - male elbow and condensate collector are
supplied in a separate pack (Fig. 12). Also in the
pack are two terminals and fixing screws for use
with separate termination installations (see
Section 7.13, Fig. 15).
2. The remainder of the flue system must be
purchased separately according to the
requirements of the installation and type of
termination (see Section 7.12)
7.10 Terminal Guard (Fig. 13)
1. When codes of practice dictate the use of
terminal guards, they can be obtained from most
Plumbers’and Builders’Merchants.
2. There must be a clearance of at least 50mm
between any part of the terminal and the guard.
3. When ordering a terminal guard, quote the
appliance model number.
4. The flue terminal guard should be positioned
centrally over the terminal and fixed as
illustrated.
7.11 Condensate Drain (Fig. 14)
1. It is necessary to incorporate the condensate
trap elbow in the flue duct of all installations.
2. The outlet on the condensate collector is
intended to accept a 12mm ID PVC pipe. Where
possible this should discharge into the household
drainage system, preferably terminating
internally. If this is not practical, discharge into an
outside gulley or soak away is acceptable. To
prevent blockage of the condensate pipe due to
freezing it should be routed internally as far as
possible.
3. The pipe should have a fall over its’entire
length of at least 10mm/metre run to ensure
effective disposal of condensate. It must also
include a trap in its’length to prevent leakage of
combustion products.
4. If the condensate drain is connected to the
drainage system within the dwelling a further trap
must be included downstream of the air break.
5. Further information on condensate discharge
is given in the British Gas document “Guidance
Notes For The Installation Of Domestic Gas
Condensing Boilers”.
Fig. 12
Fig. 13
Condensate Collector
90°Male - Male
Elbow
Flue Duct Adaptor
Air Duct Adaptor
To Boiler
Loop
Pipe from Collector
Air Break
110mm Soil
Pipe or Drain
Air Gap
30mm Min
Air Break
Strap-on Boss
10mm/metre run min fall
10mm/metre run min fall
Fig. 14

7.0 Site Requirements
16
No. Description Part No.
1. Straight Extension 0.25m 246135
2. Straight Extension 0.5m 246136
3. Straight Extension 1.0m 246137
4. 90°Elbow 246139
5. 45°Elbow (pair) 246138
6. Roof Terminal 4G 246140
7. Flat Roof Flashing (not shown) 246144
7. Universal Lead Tile 35/55 Roof Pitch 246142
7. Universal Lead Tile 25/45 Roof Pitch 246141
7. Roof Cover Plate Kit (not shown) 246143
8. Pipe Support 80mm 238684
9. Roof Terminal Adaptor - Twin 247922
7.12 Flue Components
4
1,2,3
1,2,3
1,2,3
1,2,3
1,2,3
4
5
5
5
5
5
1,2,3
1,2,3
4
1,2,3
1,2,3
4
7
6
9
Flue and Air
Duct Adaptors
*
Items marked *are supplied with each boiler in a separate pack marked
Twin Flue Adaptor Kit (Maxflue) Part No 248338
90°Male-Male
Elbow
*
Condensate
Collector
*
Terminal
*
Terminal
*
Condensate
Collector
*
90°Male-Male
Elbow
*
Flue and Air
Duct Adaptors
*

17
7.0 Site Requirements
7.13 Flue Options
1. The Baxi Combi 80 Maxflue can be fitted with
flue systems as illustrated (Figs. 15 & 16).
2. Maximum permissible equivalent flue lengths
are:-
Vertical Roof Terminal 15m
Separate Terminals 70m
IMPORTANT: When installing a flue system
with separate terminals the air duct must not
exceed 15m.
3. The term Equivalent Flue Length means the
actual physical length of flue and air pipe from
boiler to terminal(s), plus the addition of a length
factor for any bends in the flue system. This
factor represents the resistance of the bend
expressed as an equivalent straight length.
4. When using 80Øtwin flue pipe each 45°bend
is equivalent to 0.25m of straight pipe. A 90°
bend is equivalent to 0.5m.
5. If an appliance is installed with separate flue
terminals the maximum equivalent length is 70m.
The flue and air duct lengths are calculated
separately, with the proviso that the air duct
cannot exceed 15m. If the air duct was only 3m
the flue duct could be up to 67m.
6. When calculating the equivalent length of a
twin pipe system connected to a single vertical
terminal the physical length is NOT that of both
pipes, but that from boiler to terminal. However,
all bends in each leg of pipe must be considered
in the calculation.
Worked Example:-
Separate Terminal Installation
Air Duct Length = 6.0m
Flue Duct Length = 15.5m
3 off - 45°Bends at 0.25m each
2 off - 90°Bends at 0.5m each
The sum is therefore:-
6.0 + 15.5 + (3 x 0.25) + (2 x 0.5) =
6.0 + 15.5 + 0.75 + 1
Total Equivalent Length = 23.25m
Fig. 15
Fig. 16
15m Max
L1+ L2= 70m Max
(L1= 15m Max)
L2
L1

8.0 Installation
18
8.1 Initial Preparation
The gas supply, gas type and pressure must be
checked for suitability before connection (see
Section 7.6).
1. After considering the site requirements
(see Section 7.0) position the fixing template
(Fig. 17) on the wall ensuring it is level both
horizontally and vertically.
2. Mark the position of the two most suitable
fixing slots for the wall plate and boiler lower
fixing holes. It is preferable to use the horizontal
fixing slots.
3. Note the shaded area on the template.
Pipework may be routed upwards behind the
boiler, providing it does not conflict with the
shaded area.
4. If required, mark the position of the gas and
water pipes. Remove the template.
5. Drill the wall as previously marked to accept
the wall plugs supplied. Secure the wall plate
using the fixing screws.
6. Using a spirit level ensure that the plate is
level before finally tightening the screws.
7. Connect the gas and water pipes to the valves
on the wall plate using the copper tails supplied.
Ensure that the sealing washers are fitted
between the connections.
8.2 Flushing
1. Connect a tube to the central heating flow or
return pipe (Fig. 18).
2. Flush thoroughly (see System Details, Section
6.2).
8.3 Preparing The Boiler
1. Remove all packaging.
2. Stand the boiler on its base by using the rear
lower edge as a pivot.
NOTE: A small amount of water may drain
from the boiler in the upright position.
Baxi UK Limited declare that no substances
harmful to health are contained in the
appliance or used during construction of
the appliance.
Fig. 17
Fig. 18
Combi
FIXING
TEMPLATE
5 mm Minimum
Side Clearance
5 mm Minimum
Side Clearance
Horizontal Side Flue
Centre Line
107mm Dia Minimum
Aperture For Flue Tube
200 mm
Minimum
Clearance
200 mm
Minimum
Clearance
Profile of
Outercase
Vertical Flue
Centre Line
General
Area For
Electrical
Supply
Hot Water
Outlet
(15mm)
Cold Water
Inlet
(15mm)
Heating
Return
(22mm)
Heating
Flow
(22mm)
Pressure Relief
Valve
(15mm)
Gas
Inlet
(22mm)
95 mm 65 mm
Boiler Mounting Bracket Fixing Slots
Drill 8 mm diameter x 50 mm deep
65 mm 65 mm 65 mm 65 mm
Boiler Lower Fixing Holes
Drill 8 mm diameter x 50 mm deep
921.724.1
Comp No 247934 - Iss 1 - 7/00
80e Model Only
Alternative Flue Aperature
Using Rear Flue Kit
Part No. 247940
IMPORTANT
Keep rear routed pipework, clips
and electrical cables clear of all
shaded areas to allow the
correct fitting of the boiler chassis
Fixing Template
Appliance Wall Plate
Central Heating Return
Flushing Tube Wall Plate

8.0 Installation
19
8.4 Fitting The Boiler
1. Remove the sealing caps from the boiler
connections.
2. Lift the boiler using the lower edges. Engage
the slots at the top rear of the boiler on the wall
plate (Fig. 19).
3. Insert the sealing washers between the valves
and pipes on the wall plate and the boiler
connections. The rubber washers must be
used on the gas connections.
4. Tighten all the connections.
5. Secure the boiler side panels to the boiler wall
plate flanges using the screws provided (Fig. 19).
8.5 Fitting the Pressure Relief
Discharge Pipe (Fig. 20)
1. Remove the discharge pipe from the kit.
2. Determine the routing of the discharge pipe in
the vicinity of the boiler. Make up as much of the
pipework as is practical, including the discharge
pipe supplied.
3. The pipework must be at least 15mm diameter
and run continuously downwards to a discharge
point outside the building. See section 6.7 for
further details.
4. Utilising one of the sealing washers, connect
the discharge pipe to the adaptor and tighten the
nut.
5. Complete the discharge pipework and route it
to the outside discharge point.
IMPORTANT: Make all soldered joints before
connecting to the pressure relief valve.
Fig. 20
Fig. 19
Pressure Relief Valve
Wall Plate
Discharge Pipe

8.0 Installation
20
8.6 Fitting The Flue
1. Sections 7.12 and 7.13 give details of available
flue components, equivalent flue lengths etc.
2. The flue and air duct adaptors must be fitted to
the boiler outlet adaptor and boiler top panel
(Fig. 21).
3. Pass the seal over the flue duct adaptor.
Engage the 60mm diameter end of the flue duct
adaptor on the boiler outlet adaptor and slide the
seal down so that it equally covers the joint
(Fig. 22).
4. Fit the clip over the adaptors and seal, and
tighten the securing screws. Where possible
position the clip so that the screws are not visible.
5. After determining the routing of the air duct
remove the appropriate blanking plate from the
boiler top panel, being careful not to damage the
gasket. Retain the gasket and screws (Fig. 21).
6. Insert the plastic air shutter into the hole in the
top panel. Ensure that the locating dog on the
shutter locates in the notch in the top panel
(Figs. 22 & 22a).
7. Replace the gasket previously removed and fit
the air duct adaptor, ensuring that the pointer on
the adaptor aligns with the markings on the top
panel (Fig. 22).
8. Engage the air duct adaptor securing screws
but do not tighten them. The pointer on the
adaptor must align with one of the three
numbered marks on the top panel depending on
flue length. This will give the correct air inlet
restriction.
Total Equivalent Top Panel
Flue Length Mark
0 to 15m 1
15 to 30m 2
30 to 70m 3
9. Rotate the adaptor so that the pointer aligns
with the appropriate numbered mark and fully
tighten the securing screws (Fig. 23).
1
2
-
+
3
1
2
-
+
3
Clip
Flue Duct
Adaptor
Seal
Air Duct
Adaptor
Gasket
Air Shutter
Blanking Pipe
Gasket
Air Duct Adaptor
Fig. 21
Fig. 22
Fig. 23
2
-
+
3
Notch
Fig. 22a
Locating Dog
Boiler Outlet
Adaptor
Boiler Outlet
Adaptor